1. Field of the Invention
The present invention relates to a positioning apparatus, an exposure apparatus, and a device manufacturing method.
2. Description of the Related Art
The wafer stage mechanism and reticle stage mechanism of an exposure apparatus used in a lithography process to manufacture a semiconductor device are required to move the stages at a high acceleration speed and position them with high accuracy in order to improve productivity. Many exposure apparatuses therefore use coarse and fine moving stage mechanisms. A coarse and fine moving stage mechanism is configured such that a fine moving stage which is positioned with high positioning accuracy but moves with a small stroke is arranged on a coarse driving stage which is driven with a large stroke and large thrust but is positioned with low positioning accuracy.
Japanese Patent No. 4323759 discloses an arrangement in which a fine moving stage is mounted on a coarse moving stage which is driven in the X- and Y-axis directions within a horizontal plane by feedback control. A supporting unit supports the weight of the fine moving stage. The supporting unit includes a repulsion mover coupled to the fine moving stage and a repulsion stator coupled to the coarse moving stage.
Since the coarse moving stage is larger in size than the fine moving stage, it is difficult to increase the band of a feedback control system for controlling the position of the coarse moving stage. In addition, wirings and pipes mounted on the fine moving stage are received by the coarse moving stage and are then coupled to the outside. For this reason, the feedback control system of the coarse moving stage is externally disturbed by these wirings and pipes upon driving the coarse moving stage. Due to these reasons, the error of the coarse moving stage can be, for example, about 10 times that of the fine moving stage. The difference in error between the two stages will cause variations in the relative position between the repulsion stator and repulsion mover of the supporting unit. The variations in this relative position can be disturbances on control on the fine moving stage.